Re: Impossible compilation scenario!! (possible BUG)
Abdulla Herzallah wrote:
It seems that the forward declaration does not work if the class is used in
the inheritance declartion statment
the code below (compiled in Native C++ Console application) illustrate it
(as this does not work in VS2008 and that it is the latest compiler I assume
then, that VS2005 will not work either (but I have not tried it on VS2005)
What I could be missing some compiler directive!!! well please help me
here guys ( I am desperate now)
The error I keep getting C2504 Base class undefined
No matter what I tried to re-arrange the order of these classes I get the
same error for one of these classes
below is the complete code (i.e. no .h files to include in the stdfx.h)
#include "stdafx.h"
template<typename T> class Base; // forward declaring Base
class First : Base<First> { }; // >>breaking here as Base class is
undfined<<
template <typename T> class Second: First { };
template<typename T> class Base: Second<T> { };
int _tmain(int argc, _TCHAR* argv[])
{
return 0;
}
Abdulla:
This has nothing to do with templates. A class must be completely
defined in order to be used as a base or (non-pointer) member. If it is
not, the complier cannot know the size or layout of the derived class.
Forward declaration only works when the original class is only used in
the new class as a pointer or reference (or as the return type of a method).
--
David Wilkinson
Visual C++ MVP
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